Bi-directional Underactuated Exoskeleton for Finger Actuation
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Solution Overview
Problem
Traditional exoskeletons for the upper limbs face challenges in actuation, particularly in transmitting bidirectional force to each finger for optimal operation, leading to high complexity, weight, and cost due to the need for multiple actuators and sensors, which complicates force distribution and coordination among fingers.
Innovation Solution
A wearable actuation device with a single motor and transmission system using a movable member and a pair of cables, allowing for reversible actuation to assist both opening and closing of fingers, reducing size and weight through a pulley system that orients cables in compact spaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If all degrees of freedom of the hand are actively assisted with separate actuators, then the force transmission and control precision are improved, but the device complexity, weight, and cost increase significantly
Solution Approach 1:
The patent combines multiple actuation functions into a single actuator that controls all fingers through a common transmission system. The single actuator integrates the functions of multiple independent actuators, reducing device complexity while maintaining coordinated control of all fingers through shared mechanical elements like cables and pulleys.
Solution Approach 2:
The single actuator serves multiple functions by simultaneously controlling flexion and extension of multiple fingers. The transmission system is designed to distribute force from one actuator to multiple fingers, making the actuator universal in its ability to assist various hand movements without requiring separate actuators for each finger.
2Power
If passive elements like springs are used to assist finger opening, then the actuator size is reduced, but the force modulation and control precision during passive phase are lost
Solution Approach 1:
The transmission system dynamically adapts its mechanical advantage ratio during operation. As the finger moves through its range of motion, the cable-pulley geometry changes, automatically adjusting the force transmission characteristics. This dynamic adjustment allows the system to provide appropriate force modulation without requiring active control during passive movement phases.
Solution Approach 2:
The cable-pulley transmission system acts as an intermediary between the actuator and the finger, providing mechanical transformation and force modulation. The pulley system translates actuator motion into controlled finger movement with automatic force adjustment, serving as a mechanical mediator that eliminates the need for active force control during passive phases.
3Force
If rigid connections are used to transmit force and movement, then the force transmission efficiency is improved, but the device size and weight increase
Solution Approach 1:
The patent uses flexible cables instead of rigid connections to transmit force from the actuator to the fingers. These cables are lightweight yet sufficiently strong to transmit the required forces, significantly reducing device weight compared to rigid mechanical linkages while maintaining adequate force transmission efficiency for assisting hand movements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables efficient, compact, and reversible actuation of fingers with a single motor, improving coordination and reducing the complexity and cost associated with traditional systems, while maintaining effective force transmission for both flexion and extension movements.
Implementation Method 1
a motor (11), provided with an output shaft (110), supported by the supporting platform (10) and suitable to generate a rotation motion in two opposite directions of the motor shaft (110)
Implementation Method 2
a structure that, through a mechanical cable/pulley system, allows to obtain a movement of the fingers of one hand in a synergistic and adaptive way
Data Source
AI summary
The present invention relates to a wearable actuation device (1) for the assisted movement of the fingers of a user's hand, comprising a supporting platform (10), intended to be positioned on the back of the hand and provided with fixing means for wearing in a removable way the device (1) on the hand. The device also comprises at least an articulated first finger module (2), connected with one end to the supporting platform (10) and suitable to be positioned and connected to a finger of the hand for guiding a movement of flexion or extension of the finger itself, and a motor (11) provided with an output shaft, supported by the supporting platform (10) and suitable to generate a rotational motion in two opposite directions of the motor shaft (11). The device (1) also comprises first transmission means of the first finger module (2) to allow an actuation at least of the first finger module (2).